“…Presently, OER catalysts compatible with PEMWE technology predominantly depend on iridium (Ir) and ruthenium (Ru)-based materials. , Ruthenium dioxide (RuO 2 ) is widely recognized as an acidic OER electrocatalyst due to its remarkable activity and relatively abundant reserves. However, the irreversible conversion of RuO 2 to soluble RuO 4 species in acidic media severely compromises its stability, which is closely linked to the reaction process. − Currently, the prevailing OER mechanisms can be primarily classified into two pathways, namely, the lattice oxygen mechanism (LOM) and the adsorption evolution mechanism (AEM), depending on the origin of oxygen molecules in the reaction products. − The AEM pathway is distinct from the LOM pathway in that it does not consume lattice oxygen or produce oxygen vacancies, thereby maintaining the structural integrity of the catalyst during the reaction and resulting in enhanced stability. − Clearly, the structural-stability optimization of the catalyst hinges on maximizing the dominance of the AEM . To this end, defect engineering, including atomic vacancies (RuO 2 /SnO 2 ), interstitial (C-RuO 2 –RuSe), solute atoms (Ru 0.5 Ir 0.5 O 2 ), amorphous/crystalline interface (Am–Ir 1 Ru 3 O 8 ), and so on, has received considerable attention. − It is worth noting that the presence of defects can disrupt the initial structural arrangement, therefore serving as active sites to alter the pathway of the reaction process.…”